Backup pad

ABSTRACT

A method of tuning the contact pressure across an abrasive disc is presented. The method includes coupling the abrasive disc to a backup pad comprising a pressure tuning feature that causes an experienced pressure by a worksurface, across a radius of the abrasive disc, to be uniform. The method also includes abrading a worksurface by contacting the abrasive disc to the worksurface. The backup pad causes the abrasive disc to have a cut rate that is substantially uniform across the surface of the abrasive disc when compared to the abrasive disc on a backup pad with no pressure tuning feature.

BACKGROUND

Abrasive fiber discs typically have an abrasive layer on a vulcanizedfiber backing. In one common use, an abrasive fiber disc is mounted to abackup pad that is driven by a rotating power shaft of an angle grinder.The backup pad allows the operator to exert pressure toward aworksurface being abraded while mitigating pressure, angle and surfacevariation. Some such backup pads have raised ridges that can increasepressure and provide channels for escaping debris against a worksurfacebeing abraded compared to adjacent portions of the disc, resulting inincreased abrading rate. When abrasive discs are worn out and changed,they are removed from a backup pad, which can often be reused severaltimes prior to being discarded.

SUMMARY

A method of managing the contact pressure across an abrasive disc ispresented. The method includes coupling the abrasive disc to a backuppad comprising a pressure tuning feature that causes an experiencedpressure by a worksurface, across a radius of the abrasive disc, to beuniform. The method also includes abrading a worksurface by contactingthe abrasive disc to the worksurface. The backup pad causes the abrasivedisc to have a cut rate that is substantially uniform across the surfaceof the abrasive disc when compared to the abrasive disc on a backup padwith no pressure tuning feature.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numeralsmay describe similar components in different views. The drawingsillustrate generally, by way of example, but not by way of limitation,various embodiments discussed in the present document.

FIGS. 1A-1C illustrate an abrasive disc assembly mounted on a driveshaft of a power tool and parameters related thereto.

FIGS. 2A-2E illustrate an abrasive disc mounting assembly with anonuniform thickness pressure tuning feature.

FIGS. 3A-3B illustrate an abrasive disc mounting assembly with aconcentric ring pressure tuning feature.

FIGS. 4A-4C illustrates an abrasive disc mounting assembly with anonuniform surface.

FIG. 5 illustrates a method of providing a uniform cut rate inaccordance with embodiments herein.

FIG. 6 is a robotic paint repair schematic in which embodiments of thepresent invention are useful.

FIG. 7 illustrates an exploded view of the components of a robotic paintrepair stack.

FIGS. 8A-8B illustrate a tool for a robotic abrasive operation and acorresponding pressure profile.

FIGS. 9A-9G illustrate tools for providing a patterned cut rate with arobotic repair unit in accordance with embodiments herein.

FIG. 10 illustrates a method of providing a patterned cut rate with arobotic abrading system in accordance with embodiments herein.

FIGS. 11-14 relate to Example and Comparative Example constructions andresults discussed in greater detail in the Example section below.

DETAILED DESCRIPTION

In this application, the terms “compressible” or “incompressible” refersto a material property, i.e., compressibility, of an object (e.g., anelastomer outer layer) which is a measure of the relative volume changeof the material in response to a pressure. For example, the term“substantially incompressible” refers to a material having a Poisson'sratio greater than about 0.45.

The term “elastically deformable” refers to a deformed object (e.g., aninner layer of synthetic foam) being capable of substantially 100%(e.g., 99% or more, 99.5% or more, or 99.9% or more) recovering to itsoriginal, undeformed state.

In this application, the terms “polymer” or “polymers” includeshomopolymers and copolymers, as well as homopolymers or copolymers thatmay be formed in a miscible blend, e.g., by coextrusion or by reaction,including, e.g., transesterification. The term “copolymer” includesrandom, block and star (e.g. dendritic) copolymers.

The term “pressure tuning feature” as used herein refers to a componentof an abrasive backup pad assembly. This feature is mounted permanentlyor temporarily on a side of a hard backup component of the assembly,opposite to a spindle on the other side of the hard backup componentwhich is used to connect the assembly to a power tool. An abrasive discis mounted on the free surface of the “pressure tuning feature” apartfrom the hard backup component in an abrasive process. The “pressuretuning feature” is substantially softer than the hard backup componentof the assembly and thus it experiences substantial deformation comparedto the hard backup component when the assembly is engaged to aworksurface in an abrasive process. The main roles of the “pressuretuning feature” in an abrasive backup pad assembly during an abrasiveprocess includes, but is not limited to, distributing contact pressureuniformly between the pad assembly and a desired portion of theworksurface where material is supposed to be removed from, dampening thecontact pressure variation caused by disturbances such as irregularitiesin the worksurface, inhomogeneities in the abrasive disc, vibration ofthe abrasive power tool, as well as heat and debris management.

In this application, the terms “about” or “approximately” with referenceto a numerical value or a shape means +/−five percent of the numericalvalue or property or characteristic, but expressly includes the exactnumerical value. For example, an elastic modulus of “about” 200 psirefers to an elastic modulus from 190 to 210 psi, but also expresslyincludes an elastic modulus of exactly 200 psi.

In this application, the term “substantially” with reference to aproperty or characteristic means that the property or characteristic isexhibited to a greater extent than the opposite of that property orcharacteristic is exhibited. For example, a substrate (e.g., web) thatis “substantially” transparent refers to a substrate (e.g., web) thattransmits more radiation (e.g. visible light) than it fails to transmit(e.g. absorbs and reflects). Thus, a substrate (e.g., web) thattransmits more than 50% of the visible light incident upon its surfaceis substantially transparent, but a substrate (e.g., web) that transmits50% or less of the visible light incident upon its surface is notsubstantially transparent.

Referring now to FIGS. 1A and 1B, a typical abrasive disc mountingassembly 100 comprises a backup pad 110 and a clamp assembly 140 thatsecures an abrasive disc 20. The connection can be threaded, keyed,bolted, friction or any number of suitable fastener options known tothose in the art. An abrasive disc mounting assembly 100 includes anoutwardly facing centrally disposed fastening member 130 (shown as athreaded bore, see FIG. 4 ) that is adapted to engage a threaded driveshaft 10 of a power tool (not shown) such as, for example, an anglegrinder. The backup pad 110 may have ribbed projections on adisc-engaging surface that provide added support to abrasive disc 20.During abrading of a worksurface, the drive shaft 10 rotates around arotational axis of use (115).

Because abrasive disc 20 spins in direction 30 during an abradingoperation, as illustrated in FIG. 1C, both a linear velocity profile 40and a material removal rate profile 50 (assuming constant appliedpressure between abrasive disc 20 and a worksurface) show a higherlinear velocity, and a higher removal rate as a distance from the disccenter increases. This causes uneven cut rate across the surface ofabrasive disc 20 increasing from the disc center toward the discperimeter. Additionally, the wear on abrasive disc 20 is uneven, withfaster wear occurring on the exterior and as the abrasive disc wearsdown, it causes still more uneven cut rate across the surface of theabrasive disc. For human-operated abrasive operations, it is oftendesired to have a uniform cut rate along a radius extending from acenter to an edge of an abrasive disc. However, it is expresslycontemplated that, for some abrasive operations it may be desired tohave a patterned cut rate other than uniform. While the embodimentsdiscussed in FIGS. 2-7 are directed towards achieving a patterned cutrate that is uniform across a surface of an abrasive disc 20, it isexpressly contemplated that one having skill in the art could adapt themto result in an uneven or other patterned cut rate. For example, apatterned cut rate may be useful for managing debris removal, heatgeneration, blending of cut rate, feathering a cut rate, reduction insecondary scratching and haze avoidance.

FIGS. 1A and 1B illustrate a cone-shaped backup pad 110. However, it isexpressly contemplated that other backup pad designs may also benefitfrom the embodiments discussed herein. For example, FIGS. 3A-3Billustrate a flat backup pad 304. Different backup pad designs andconstruction may be useful for different applications. For example, acone design may be useful for volume displacement when significantmaterial is being removed or added. Additionally, different materialconstruction may be important for the compressibility or flexibilityneeds of a given application.

FIGS. 2A-2E illustrate an abrasive disc mounting assembly with anonuniform thickness pressure tuning feature. FIG. 2A is a perspectiveview of assembly 200, which includes a spindle 210 coupled to a conicalbackup pad 220, which in turn is coupled to a pressure tuning feature230 with a conical shape cavity, which substantially matches the conicalbackup pad 220, on a first side. Pressure tuning feature 230 couples tothe backup pad 220 on a first side and, on an opposite side 240,receives an abrasive disc. Abrasive-receiving side 240 is, in someembodiments, substantially flat, as illustrated in FIGS. 2B and 2C. FIG.2B illustrates a side view 225 of assembly 200. FIG. 2C illustrates acutaway view 250 of assembly 200 along section line 2C-2C illustrated inFIG. 2B. As illustrated, pressure tuning feature 230 substantiallyequalizes a depth 224 of the backup pad 220 along a width 222 ofassembly 200.

FIG. 2D illustrates a graph of contact pressure along a radius of abackup pad designed like that of FIG. 2C against a worksurface. Asillustrated, the contact pressure decreases along the radius of thebackup pad from disc center toward its perimeter.

FIG. 2E illustrates an example relative composition of the backup pad280 and the pressure tuning feature 290, for example as a cutaway viewsimilar to the view 250. As a relative portion of height 294corresponding to the pressure tuning feature 290 decreases, the relativeportion of the backup pad 280 increases. In some embodiments, thepressure tuning feature 290 is at least a portion of depth 294 along theentire radius 272. In some embodiments, surface 284 of pressure tuningfeature 290 is straight. An abrasive disc 286 can be mounted on surface284 of pressure tuning feature 290. In some embodiments, interface 282between backup pad 280 and pressure tuning feature 290, at any pointalong radius 272, is straight with a constant slope. The slope ofinterface 282 can be selected based on a desired profile for contactpressure on abrasive disc 286 along radius 272 when the pad assembly 270is compressed against a worksurface in an abrasive process. Even thoughit is not illustrated in FIG. 2E, in some embodiments pad assembly 270can include channels extended between surface 284 of pressure tuningfeature 290, where an abrasive disc is mounted, and the opposite surfaceof the assembly on backup pad 280 for dust and debris extraction.

The exact composition and hardness of pressure tuning feature 290 canvary based on a desired contact pressure profile between abrasive disc286 and a worksurface during an abrasive process. Lower contactpressures can be obtained by using a softer material. Also, morevariation in the thickness of pressure tuning feature 290 across the padradius causes more variation in contact pressure across the pad whichmight be required to obtain a desired cut profile.

Components of both backup pad 280 and pressure tuning feature 290 shouldbe made of appropriately durable materials. Examples of materials forbackup pad 280 include engineering plastics (e.g., nylons, polyphenylenesulfide, polyether ketone, polyether ether ketone, polycarbonate, highdensity polyethylene, high density polypropylene, polyester,polyurethane, etc.), polymer composites, metals, ceramic composites, andcombinations thereof.

The material used for pressure tuning feature 290 may be substantiallysofter than the material used for backup pad 280. This softness may beprovided in several ways, for example by choosing a material with alower hardness (as indicated using any appropriate hardness scale, suchas Shore A or Shore OO), by choosing a material with a lower elasticmodulus, by choosing a material with a higher compressibility (typicallyquantified via a material's Poisson's ratio), or by modifying thestructure of the softer material to contain a plurality of gasinclusions, such as a foam or an engraved structure, etc. In someembodiments, the pressure tuning feature 290 can include a materialhaving a hardness of less than about 50 Shore A, less than about 40Shore A, and optionally less than about 40 Shore A (as measured usingASTM D2240). In some embodiments, the materials used in the pressuretuning feature 290 may have an elastic modulus of less than about 500psi, less than about 400 psi, or optionally less than about 200 psi. Insome embodiments, the compressibility of the pressure tuning feature 290may be measured via Compression Force Deflection Testing per ASTM D3574when the pressure tuning feature is foam; and via Compression-DeflectionTesting per ASTM D1056 when the pressure tuning feature is a flexiblecellular material such as, for example, sponge or expandable rubber. Thepressure tuning feature 290 may have a compressibility of less thanabout 60 psi at 25% deflection, optionally less than about 45 psi at 25%deflection. The pressure tuning feature 290 is configured to beelastically deformable, e.g., being capable of substantially 100% (e.g.,99% or more, 99.5% or more, or 99.9% or more) recovering to its originalstate after being deformed. In some embodiments, the pressure tuningfeature 290 can be compressible (i.e. having a Poisson's ratio of lessthan 0.2 or less than 0.1) to provide the desired deformability. In someembodiments, the pressure tuning feature 290 may be substantiallyincompressible, e.g., the relative volume change of the material inresponse to a contact pressure is less than 5%, less than 2%, less than1%, less than 0.5%, or less than 0.2%, but sufficiently soft to providethe desired deformability. In some embodiments, the pressure tuningfeature 290 may be a made of a substantially incompressible materialwhich has been patterned, 3D printed, embossed, or engraved to providethe desired deformability. In some embodiments, the pressure tuningfeature 290 can have a Poisson's ratio less than about 0.5, less thanabout 0.4, less than about 0.3, or preferably less than about 0.2. Insome embodiments, the pressure tuning feature 290 can have a negativePoisson's ratio.

In some embodiments, the pressure tuning feature 290 can include one ormore materials of a foam, an engraved, structured, 3D printed, orembossed elastomer, a fabric or nonwoven layer, or a soft rubber. Asuitable foam can be open-celled or closed-celled, including, forexample, synthetic or natural foams, thermoformed foams, polyurethanes,polyesters, polyethers, filled or grafted polyethers, viscoelasticfoams, melamine foam, polyethylenes, cross-linked polyethylenes,polypropylenes, silicone, ionomeric foams, etc. The pressure tuningfeature 290 may also include foamed elastomers or vulcanized rubbers,including, for example, isoprene, neoprene, polybutadiene, polyisoprene,polychloroprene, nitrile rubbers, polyvinyl chloride and nitrile rubber,ethylene-propylene copolymers such as EPDM (ethylene propylene dienemonomer), and butyl rubber (e.g., isobutylene-isoprene copolymer). Asuitable foam pressure tuning feature 290 can have a compressibility,for example, less than about 60 psi at 25% deflection, or less thanabout 45 psi at 25% deflection. It is to be understood that the pressuretuning feature 290 may include any suitable compressible structures suchas, for example, springs, nonwovens, fabrics, air bladders, etc. In somepressure tuning feature 290 can be 3D printed to provide desiredPoisson's ratio, compressibility, and elastic response.

Additionally, while a single pressure tuning feature 290 is illustrated,it is expressly contemplated that feature 290 may be made of multiplelayers and/or multiple materials in a layered or agglomerateconstruction.

FIGS. 3A-3B illustrate an abrasive disc mounting assembly with aconcentric ring pressure tuning feature. FIGS. 3A and 3B illustratedifferent perspective views of assembly 300, which includes a spindle302, backup pad 304, and pressure tuning feature 350. As illustrated inFIG. 3A, the pressure tuning feature includes multiple concentric rings.While three rings 310, 320 and 330 are illustrated in FIG. 3A, it isexpressly contemplated that, in other embodiments, only two rings arepresent, or more rings, such as four, five, six, eight, ten, or evenmore, are present.

In one embodiment, as illustrated in FIG. 3A, of an overall radius 306,each ring 310, 320, 330 occupies an equal portion, each having an equalradial depth 312, 322, 332 across pressure tuning feature 350. Thepressure tuning feature 350 can also be a single piece with gradual orstepwise hardness change from the center to the edge of the pad. Usingan adhesive layer, a hook-and-loop mounting system, or another suitableappropriate mounting system, an abrasive disc can be mounted on thesurface of the pressure tuning feature 350 away from the backup pad 304in abrasive applications. One advantage of the assembly 300 is that thevariation of the stiffness or hardness from the center to the edge ofthe pressure tuning feature 350 can be adjusted to account for thelinear velocity variation across the pad, as indicated by element 40 inFIG. 1C, and provide a uniform cut rate across the pad in abrasive orpolishing applications.

Each of rings 310, 320 and 330, in one embodiment, vary in theirmaterial properties. In one embodiment, rings increase in materialsoftness as a radial distance from the center increases. Each ring maybe made of a different material than an adjoining ring, such that thesoftness of adjacent rings increases from the center to the exterior ofthe backup pad.

This softness may be provided in several ways, for example by choosing amaterial with a lower hardness (as indicated using any appropriatehardness scale, such as Shore D, Shore A or Shore OO), by choosing amaterial with a lower elastic modulus, by choosing a material with ahigher compressibility (typically quantified via a material's Poisson'sratio), or by modifying the structure of the softer material to containa plurality of gas inclusions, such as a foam or an engraved structure,etc. For example, when ring 330 and 320 in the assembly 300 includematerials having a hardness of 60 and 40 Shore A (as measured using ASTMD2240) respectively, then the hardness of rings 310 may be less than 40Shore A. It should be noted that in some cases the hardness may be mostappropriately measured using different scales for pressure tuningfeature 350 (e.g., Shore A or Shore OO). In some embodiments, thecompressibility of the materials used in pressure tuning feature 350 maybe measured via Compression Force Deflection Testing per ASTM D3574 whenthe material is foam; and via Compression-Deflection Testing per ASTMD1056 when the material is a flexible cellular material such as, forexample, sponge or expandable rubber. The materials used to the pressuretuning feature 350 may have an elastic modulus of less than about 650psi, less than about 500 psi, or optionally less than about 400 psi. Thepressure tuning feature 350 may include materials with a compressibilityin the range of 10 to 170 psi at 25% deflection. The pressure tuningfeature 350 is configured to be elastically deformable, e.g., beingcapable of substantially 100% (e.g., 99% or more, 99.5% or more, or99.9% or more) recovering to its original state after being deformed. Insome embodiments, some materials used in the pressure tuning feature 350can be compressible (i.e. having a Poisson's ratio of less than 0.2 orless than 0.1) to provide the desired deformability. In someembodiments, some materials used in pressure tuning feature 350 may besubstantially incompressible, e.g., the relative volume change of thematerial in response to a contact pressure is less than 5%, less than2%, less than 1%, less than 0.5%, or less than 0.2%, but sufficientlysoft to provide the desired deformability. In some embodiments, somematerials used in the pressure tuning feature 350 may be made of asubstantially incompressible material which has been patterned, 3Dprinted, embossed, or engraved to provide the desired deformability.

In some embodiments, the pressure tuning feature 350 can includematerials with a hardness of less than about 60 Shore A, less than about40 Shore A, or even less than about 30 Shore A. In some embodiments, thematerials used in the pressure tuning feature 350 can have a Poisson'sratio less than about 0.5, less than about 0.4, less than about 0.3, oreven less than about 0.2. In some embodiments, some of the materialsused in the pressure tuning feature 350 can have a negative Poisson'sratio.

In some embodiments, the pressure tuning feature 350 can include one ormore materials of a foam, an engraved, structured, 3D printed, orembossed elastomer, a fabric or nonwoven layer, or a soft rubber. Asuitable foam can be open-celled or closed-celled, including, forexample, synthetic or natural foams, thermoformed foams, polyurethanes,polyesters, polyethers, filled or grafted polyethers, viscoelasticfoams, melamine foam, polyethylenes, cross-linked polyethylenes,polypropylenes, silicone, ionomeric foams, etc. The pressure tuningfeature 350 may also include foamed elastomers or vulcanized rubbers,including, for example, isoprene, neoprene, polybutadiene, polyisoprene,polychloroprene, nitrile rubbers, polyvinyl chloride and nitrile rubber,ethylene-propylene copolymers such as EPDM (ethylene propylene dienemonomer), and butyl rubber (e.g., isobutylene-isoprene copolymer). It isto be understood that the pressure tuning feature 350 may include anysuitable compressible structures such as, for example, springs,nonwovens, fabrics, air bladders, etc. In some embodiments, at least aportion of the pressure tuning feature 350 can be 3D printed to providedesired Poisson's ratio, compressibility, and elastic response.

The backup pad 304 is substantially harder than the pressure tuningfeature 350, i.e. when the assembly 300 is used in an abrasiveapplication, the compressive deformation of the backup pad 304 isnegligible compared to that of the pressure tuning feature 350.Components of both backup pad 304 and pressure tuning feature 350 shouldbe made of appropriately durable materials. Examples of materials forbackup pad 304 include engineering plastics (e.g., nylons, polyphenylenesulfide, polyether ketone, polyether ether ketone, polycarbonate, highdensity polyethylene, high density polypropylene, polyester,polyurethane, etc.), polymer composites, metals, ceramic composites, andcombinations thereof.

FIGS. 4A-4C illustrates an abrasive disc mounting assembly with anonuniform surface. Assembly 400 includes a spindle 410, which connectsto a drive shaft of a power tool or machine. A conical backup pad 420 isconnected to spindle 410 from its flat surface 450. A pressure tuningfeature 430 is mounted on the conical side, on the opposite side of thesurface 450, of the backup pad 420. In one embodiment, the thickness ofthe pressure tuning feature 430 is uniform across the conical backuppad. An abrasive pad can be mounted on surface 440 of the pressuretuning feature 430 using an adhesive layer, a hook-and-loop mountingsystem, or other appropriate mounting systems for abrasive applications.FIG. 4A illustrates a side view of assembly 400. FIG. 4B illustrates acutaway view of assembly 400, taken along section line 4B-4B illustratedin FIG. 4A. FIG. 4C illustrates an exploded view of assembly 400. In oneembodiment, the backup pad 420 can be made of a flat piece 460 and aconical piece 436. Assembly 400 has an overall diameter 402. In someembodiments, pressure tuning feature 430 has a diameter 432 that issubstantially the same length as diameter 402. However, in someembodiments, diameter 432 is shorter than diameter 402. The conicalbackup pad 420 has a grade 434, which may be adjusted to tune thecontact pressure between an abrasive pad mounted on the surface 440 ofthe pressure tuning feature 430 and a worksurface when the abrasive padon the assembly 400 meets the worksurface in an abrasive operation.. Thegrade 434 is less than 180°. It can be, for example about 175°, about170°, about 165°, about 160°, about 155°, about 150°, about 145°, about140° or about 135°. Additionally, the grade may be shallower, forexample between about 176° and 179°.

In some embodiments, an abrasive pad on the mounting assembly 400 firstcomes to contact with a worksurface with the tip of its conical portion.By engaging the pad more against the worksurface, the other portions ofthe abrasive pad meet then the worksurface to abrade that. In thisscenario, the pressure tuning feature 430 is compressed more near theconical tip and its compression decreases toward the edge of the pad.This leads to a contact pressure profile which is maximum in the centerof the pad and decreases across the pad toward its edge. This decreasingcontact pressure can account for the increasing linear velocity profile40 illustrated in FIG. 1C and consequently help the pad to removeuniform material across the pad from its center toward its edge

In another embodiment where the goal is to abrade a small portion of aworksurface, a pad on the mounting assembly 400 provides this capabilityto only contact the desired area of the worksurface without contactingother portions of that. This capability gives also the opportunity ofusing different locations of the pad to abrade the worksurface whichleads to a longer life for the abrasive pad compared to a traditionalpad assembly with a flat surface which is used mostly from areas closeto its edge.

The material used for pressure tuning feature 430 is substantiallysofter than the material used for conical backup pad 420, i.e. when theassembly 400 is used in an abrasive application, the compressivedeformation of the backup pad 420 is negligible compared to that of thepressure tuning feature 430. The softness may be provided in severalways, for example by choosing a material with a lower hardness (asindicated using any appropriate hardness scale, such as Shore A or ShoreOO), by choosing a material with a lower elastic modulus, by choosing amaterial with a higher compressibility (typically quantified via amaterial's Poisson's ratio), or by modifying the structure of the softermaterial to contain a plurality of gas inclusions, such as a foam or anengraved structure, etc. In some embodiments, the compressibility of thepressure tuning feature 430 may be measured via Compression ForceDeflection Testing per ASTM D3574 when the pressure tuning feature isfoam; and via Compression-Deflection Testing per ASTM D1056 when thecompressible is a flexible cellular material such as, for example,sponge or expandable rubber. The pressure tuning feature 430 may have ahardness of less than about 60 Shore A, less than about 50 Shore A, andpreferably less than about 40 Shore A. The material used to the pressuretuning feature 430 may have an elastic modulus of less than about 400psi, less than about 300 psi, and preferably less than about 200 psi.The pressure tuning feature 430 may have a compressibility of less thanabout 75 psi at 25% deflection, optionally less than about 45 psi at 25%deflection. The pressure tuning feature 430 is configured to beelastically deformable, e.g., being capable of substantially 100% (e.g.,99% or more, 99.5% or more, or 99.9% or more) recovering to its originalstate after being deformed. In some embodiments, the pressure tuningfeature 430 can be compressible (i.e. having a Poisson's ratio of lessthan 0.2 or less than 0.1) to provide the desired deformability. In someembodiments, the pressure tuning feature 430 may be substantiallyincompressible, e.g., the relative volume change of the material inresponse to a contact pressure is less than 5%, less than 2%, less than1%, less than 0.5%, or less than 0.2%, but sufficiently soft to providethe desired deformability. In some embodiments, pressure tuning feature430 may be a made of a substantially incompressible material which hasbeen patterned, 3D printed, embossed, or engraved to provide the desireddeformability.

In some embodiments, the pressure tuning feature 430 can include one ormore materials of a foam, an engraved, structured, 3D printed, orembossed elastomer, a fabric or nonwoven layer, or a soft rubber. Asuitable foam can be open-celled or closed-celled, including, forexample, synthetic or natural foams, thermoformed foams, polyurethanes,polyesters, polyethers, filled or grafted polyethers, viscoelasticfoams, melamine foam, polyethylenes, cross-linked polyethylenes,polypropylenes, silicone, ionomeric foams, etc. The pressure tuningfeature 430 may also include foamed elastomers or vulcanized rubbers,including, for example, isoprene, neoprene, polybutadiene, polyisoprene,polychloroprene, nitrile rubbers, polyvinyl chloride and nitrile rubber,ethylene-propylene copolymers such as EPDM (ethylene propylene dienemonomer), and butyl rubber (e.g., isobutylene-isoprene copolymer). Asuitable foam pressure tuning feature 430 can have a compressibility,for example, less than about 75 psi at 25% deflection, optionally lessthan about 45 psi at 25% deflection. It is to be understood that thepressure tuning feature 430 may include any suitable compressiblestructures such as, for example, springs, nonwovens, fabrics, airbladders, etc. In some embodiments, the pressure tuning feature 430 canbe 3D printed to provide desired Poisson's ratio, compressibility, andelastic response.

Components of both backup pad 420 and pressure tuning feature 430 shouldbe made of appropriately durable materials. Examples of materials forbackup pad 420 include engineering plastics (e.g., nylons, polyphenylenesulfide, polyether ketone, polyether ether ketone, polycarbonate, highdensity polyethylene, high density polypropylene, polyester,polyurethane, etc.), polymer composites, metals, ceramic composites, andcombinations thereof.

The embodiments illustrated in FIGS. 2-4 are designed to achieve apatterned cut rate that is uniform across the diameter of a backup pad.This increases the overall efficiency and service life of eachindividual abrasive pad attached to the backup pad. These embodimentsalso provide a more uniform cut and surface finish on worksurfaces beingabraded by them compared to traditional pad assemblies. Each embodimentillustrated in FIGS. 2-4 are exemplary. It is expressly contemplatedthat each can be customized depending on a given abrading operation'srequirement. For example, through channels may be extended from thesurface of the mounting systems exposed to the abrasive pad to the freesurface of the backup pad in each embodiment to ease debris and dustextraction and management during abrasive applications. Additionally,each embodiment provides unique advantages.

FIG. 5 illustrates a method of providing a uniform cut rate inaccordance with embodiments herein. Method 500 may be useful with any ofthe abrasive disc mounting assemblies of FIGS. 2-4 , or with anothersuitable abrasive disc mounting design.

In block 510, an abrasive disc mounting assembly I is coupled to a tool.The tool can be a linear sander, rotary sander, orbital sander, randomorbital sander or other suitable tools. The abrasive disc mountingassembly may have, on a side opposing a tool connection side, a flatsurface 502, a conical surface 504, or another surface structure 506,such as a truncated cone.

In block 520, an abrasive pad is coupled to an abrasive disc mountingassembly that includes a backup pad coupled to a pressure tuningfeature. The abrasive pad may be coupled directly to the pressure tuningfeature, as illustrated in block 522, or directly to a backup pad, asillustrated in block 524. The abrasive pad may also be coupled to theassembly in another suitable manner, as indicated in block 526.

In block 530, an abrading operation is conducted. This may includeactuating a tool manually, as illustrated in block 527, semi-manually,as illustrated in block 528, or by other suitable methods, such as arobot, as illustrated in block 529.

FIG. 6 is a robotic paint repair schematic in which embodiments of thepresent invention are useful. While the example of a paint repair robot604 is illustrated in FIG. 6 , it is expressly contemplated that thetool and backup pad embodiments illustrated in FIGS. 2-5 and 8-10 couldbe used for applications other than paint repair.

In FIG. 6 , the respective boxes represent various hardware componentsof the system including robot controller 602, robot manipulator 604, androbotic paint repair stack 606 including compliant force control unit608, tool 610, and abrasive articles/compounds 612. The flow of data isdepicted by the background arrow 614 which starts with pre-inspectiondata module 616 that provides inspection data including identifieddefects in the substrate and ends with post-inspection defect datamodule 618 for processing data generated from the substrate 620 duringthe defect repair process.

In operation, the defect locations and characteristics are fed from thepre-inspection data module 616 to the robot controller 602 that controlsrobot manipulator 604 on which a program guides an end effector (stack)606 to the identified defect to execute some pre-determined repairprogram (deterministic) policy. In some rare cases, the policy might beable to adapt depending on the provided defect characteristics.

For paint repair applications, the robotic paint repair stack 606comprises abrasive tooling 610 and abrasive articles and compounds 612along with any ancillary equipment such as (compliant) force controlunit 608. As used herein, the robotic paint repair stack 606 is more orless synonymous with the term end effector; however, in this documentthe term “stack” is the end effector in the context of robotic paintrepair. Also, though described for providing robotic paint repair, whichincludes repair of primer, paint, and clear coats, it will beappreciated that the techniques described herein lend themselves toother industrial applications beyond paint repair.

The stack 606, in FIG. 6 , can provide feedback back to controller 602,in a feedback loop, such that operation of robot 604, compliance forcecontrol unit 608 and tool 610 can continuously adjust settings during anabrasive situation.

FIG. 7 illustrates an exploded view of the components of a robotic paintrepair stack. As illustrated, the robotic paint repair stack 606comprises a robot arm 700, force control sensors and devices 608, agrinding/polishing tool 610, a hardware integration device 702, abrasivepad(s) and compounds 612, a design abrasives process 704, and data andservices 706. These elements may work together to identify defectlocations and to implement a predetermined repair program using adeterministic policy for the identified defect, such as the policydiscussed in co-owned and co-pending PCT Application No.PCT/IB2019/057053, filed on Aug. 21, 2019.

FIGS. 8A-8B illustrate a tool for a robotic abrasive operation and acorresponding contact pressure profile of the tool against aworksurface.

FIG. 8A illustrates a tool 800 for a robotic grinding unit. Tool 800 isconnected to a rotary device via the vertical shaft 810. An abrasivearticle attaches to tool 800 on a surface of backup pad 820, on oppositeside of shaft 810 backup pad 820. Backup pad 820 is often a flexiblepad. FIG. 8B illustrates a contact pressure profile 850 that resultsfrom the tool being used against a worksurface. Even with theflexibility of the pad, the pressure profile 850 of the abrasive on thesurface is irregular. As the pressure is measured from the center of theabrasive tool 800, at approximately 9 mm from the center to 13 mm on theradius, there is a spike in pressure.

FIG. 8A illustrates a rigid bed design for tool 800, which includes afoam pad that provides flexibility for an abrasive article, connected byadhesive, hook-and-loop or mechanically, to conform to the surfacewithin the pressure profile of the backing foam. Buildup of detritusoften occurs as the tool 800 engages a work surface. This, as well asthe characteristics of the tool during high velocity abrading,contributes to the lack of uniformity in pressure.

FIGS. 9A-9G illustrate tools for providing a patterned cut rate with arobotic repair unit in accordance with embodiments herein. FIGS. 9A-9Cillustrate embodiments of tools that can directly engage a robotic, forexample using a force control unit and/or end effector in someembodiments.

Handheld power tools require that the tool accommodate the lack of motorprecision inherent in a human user. However, embodiments of toolsillustrated in FIGS. 9A-9C are useful for robotic units able to leveragethe precision and accuracy of automated abrasive tooling.

Tool 900 engages a robotic unit using shaft 902. Tool has a pad engagingsurface 910 for engaging pad 904, which engages an abrasive article.Tool surface 910 can be modified to include a pattern of apertures,illustrated in FIG. 9A as including two sizes of holes 912 and 914. Asillustrated in FIG. 9A, holes 912, 914 extend through surface 910. Holesets 912 and 914 are arranged about shaft 902, with smaller holes 912closer to the shaft than larger holes 914. In some embodiments, eachhole in a given set of holes 912, 914 is equally spaced from adjacent,similarly sized holes. Additionally, while circular holes areillustrated in FIG. 9A, it is expressly contemplated that slatsextending partly or completely through surface 910, indentationsextending partway through surface 910, or another suitable modificationthat allows for flexing of surface 910 are envisioned. Specifically, thedesign of FIG. 9A allows tool 800 to flex under speed and pressure tofacilitate a ‘feathered edge’ when a paint defect is abraded, such thatthe surface modification is not readily detectable.

However, it is expressly contemplated that design of a given tool canfacilitate specific effects (feathering, cutting edge) as well as tobetter manage detritus created during an abrading operation. The goal ofmanaging cuttings is to reduce the creation of undesired surfaceartifacts as well as to increase abrasive disk life and cuttingconsistency.

FIG. 9B illustrates an angled tool 920 which includes a shaft 922connected to an angled tool surface 930, which allows for the weakeningof the contact points at the outer edges so that more force is appliedat the center of the tool 920 and contact is weakened as the tool 900 isin contact farther out from the center of the tool.

FIG. 9C illustrates a tool 940 with a scalloped edge in addition to anangled surface. However, it is expressly contemplated that, in someembodiments, scalloped edge is present alone, without an angled surface.Tool 940 has a shaft 942, that connects to an angled tool surface 950with a plurality of scallops 952 equally spaced about the circumferenceof tool surface 950. The scallops 952 further differentiate the forcefrom the center of tool 940 to the edges as compared to tool 920.

FIG. 9D illustrates a robotic tool 962 with a foam pad 964 in anassembly 962.

FIG. 9E illustrates a flexible tool 972 with a foam pad 974 in anassembly 970. As illustrated in FIG. 9E, flexible tool has a grade 976from the spindle to an edge of the tool, such that the edge of the toolis thinner than the center of the tool, resulting in added flexibilityat the edges.

FIG. 9F illustrates a patterned tool 982 with a foam pad 982 in anassembly 980. As illustrated in FIG. 9F, tool 982 includes a pluralityof indentations 985 extending inward from a circumference of tool 982.Indentations 985, are illustrated in FIG. 9F as having two edges 988meeting at a point to form an angle 986. However, it is expresslycontemplated that rounded edges and inflection points are possible.Indentation 985 has a depth 987 extending inward from a circumference oftool 982. Indentations 985 provide some pressure relief at the outsideof tool assembly 980, which allows for better debris management at edge.Illustrated in FIG. 5F is an embodiment with four indentations spacedequidistant apart on the tool circumference. However, it is expresslycontemplated that more, or fewer, indentations might be suitable in someembodiments. For example, only two indentations 985 could be present, orthree indentations 985. Similarly, 5, 6, 7, 8, 10, 12, 16, 20 or moreindentations 985 could be present.

FIG. 9G illustrates a patterned tool 992 with a foam pad 994 in anassembly 990. Tool 992 includes a plurality of cutaway portions 993 arepresent within tool 992. As illustrated in FIG. 9G, cutaway portionsextend substantially from a circumference to a spindle radius of tool992. Cutaway portions can be defined by a length 998, extendingperpendicularly from the circumference, and a width 997. In someembodiments, width 997 is variable from a circumference to a spindle oftool 992, for example wider at the circumference than the spindle. Insome embodiments, cutaways 993 have curvature 998 at the intersection ofthe cutaway 993 with tool a tool spindle. Cutaways 993 providesignificant pressure relief for tool 992, allowing for improved debrismanagement, heat management and patterning.

While FIGS. 9F and 9G illustrate a flat tool surface extending from atool spindle, it is expressly contemplated that the indentations 985 orcutaways 993 could be combined, in other embodiments, with gradient 976to provide additional flexibility.

FIG. 10 illustrates a method of providing a patterned cut rate with arobotic abrading system in accordance with embodiments herein. Asdiscussed above, robotic abrading systems have the ability to abradesmall areas (e.g. under 35 mm in area) with fine control. Once anabrading operation has begun, a robotic control unit can adjust grindingparameters in order to increase cut rate, cut efficiency, or improveaesthetics of a work surface following a repair. Tools discussed hereincan be used to create a patterned cut rate, for example an angled cutrate where a tool is tilted during an abrading operation to cause onepoint of a contact area is cut deeper than another point. Other patternsfor cut rates are also contemplated.

In block 1010, a robotic control cell is initiated. Initiation mayinclude providing power to a robotic repair unit, moving it intoposition such that an abrasive article can engage a work surface. Theabrasive article may be urged into contact with the work surface using amotive robot arm. Pressure may be exerted, on the abrasive article,using a force control unit.

In block 1020, an abrasive operation is conducted. In some embodiments,the abrasive operation follows a preset repair plan, for exampleselected based on a desired end state of the work surface engaged. Inother embodiments, the abrasive operation follows a dynamic plan toachieve a desired outcome—e.g. desired final work surface state, desiredcut shape, work surface resistance, etc.

In block 1030, feedback is received. For example, feedback may bereceived from robot control sensor units, servo tool motor sensor unitsand/or sensor units embedded directly in the tool. Vibration may besensed by the a vision system analyzing movement of the tool duringoperation frame to frame.

In block 1040, a tool parameter is modified in-situ, such that theabrasive operation can continue. In some embodiments, the feedback isreceived and a modification is made without an abrasive tool breakingcontact with a worksurface. However, in other embodiments the tool mustdisconnect from a surface in order for sensor readings to be capturedand feedback provided.

Tool parameters that can be modified in response to feedback receivedinclude a contact pressure 1042 between a tool and a worksurface, acontact angle 144 of the tool with respect to the work surface, oranother suitable parameter. For example, rotational velocity can bemodified with respect to a tool, or a pattern of movement of the toolwith respect to the work surface, or another suitable parameter.

Abrasive discs may couple to backup pads and/or dampeners describedherein using any suitable non-permanent attachment mechanism. Forexample, an adhesive may be applied, including a pressure-sensitiveadhesive, in one embodiment. A hook-and-loop attachment may also beused, with either the hook or the loop portion on the non-abrasive sideof abrasive disc.

An abrasive disc, in one embodiment, is a coated abrasive disc includinga backing with a plurality of abrasive grains embedded within a makecoat and optionally coated with a size coat and/or a super-size coat.The backing substrate can be any of fabric, open-weave cloth, knittedfabric, porous cloth, loop materials, unsealed fabrics, open or closedcell foams, a nonwoven fabric, a spun fiber, a film, a perforated filmor any other suitable backing material. A fabric backing may includecloth (e.g., cloth made from fibers or yarns comprising polyester,nylon, silk, cotton, and/or rayon, which may be woven, knit or stitchbonded) or scrim. The abrasive grains may include shaped abrasivegrains, crushed abrasive grains, or platey shaped abrasive grains. Thesize of the abrasive grains may be selected based on the aggressivenessof the repair operation to be completed. The abrasive disc may be astiff or flexible abrasive disc.

The above-presented description and figures are intended by way ofexample only and are not intended to limit the illustrative embodimentsin any way except as set forth in the appended claims. It is noted thatvarious technical aspects of the various elements of the variousexemplary embodiments that have been described above can be combined innumerous other ways, all of which are considered to be within the scopeof the disclosure.

Accordingly, although exemplary embodiments have been disclosed forillustrative purposes, those skilled in the art will appreciate thatvarious modifications, additions, and substitutions are possible.Therefore, the disclosure is not limited to the above-describedembodiments but may be modified within the scope of appended claims,along with their full scope of equivalents.

A method of managing the contact pressure across an abrasive disc ispresented that includes coupling the abrasive disc to a backup pad. Thebackup pad includes a pressure tuning feature that causes an experiencedpressure by a worksurface, across a radius of the abrasive disc, to beuniform. The method also includes abrading a worksurface by contactingthe abrasive disc to the worksurface. The backup pad causes the abrasivedisc to have a cut rate that is substantially uniform across the surfaceof the abrasive disc when compared to the abrasive disc on a backup padwith no pressure tuning feature.

The method may be implemented such that the pressure tuning feature iselastically deformable.

The method may be implemented such that the pressure tuning feature ispositioned between the backup pad and the abrasive disc.

The method may be implemented such that the pressure tuning featureincludes a material having a hardness of less than about 60 Shore A.

The method may be implemented such that the pressure tuning featureincludes a material having a compressibility of less than about 170 psiat 25% deflection.

The method may be implemented such that the pressure tuning featureincludes a material that is compressible.

The method may be implemented such that the pressure tuning featureincludes a material that is substantially incompressible.

The method may be implemented such that the pressure tuning featureincludes a substantially incompressible material which has beenpatterned, 3D printed, embossed, or engraved.

The method may be implemented such that the pressure tuning featureincludes a foam, an engraved, structured, 3D printed, or embossedelastomer, a fabric layer, a nonwoven layer, or a soft rubber.

The method may be implemented such that the pressure tuning feature ismade of multiple layers and/or multiple materials in a layered oragglomerate construction.

The method may be implemented such that the backup pad includes channelsextended from the surface of the pressure tuning feature, where theabrasive disc is mounted, to the opposite side of the backup pad fordust and debris extraction.

The method may be implemented such that the pressure tuning featureincludes a material having an elastic modulus of less than about 650psi.

The method may be implemented such that the pressure tuning feature hasa nonuniform thickness.

The method may be implemented such that the pressure tuning feature hasa conical cavity mounted on a conical surface of the backup pad.

The method may be implemented such that the hardness of the pressuretuning feature changes across the pad from its center toward itsperimeter.

The method may be implemented such that the hardness of the pressuretuning feature changes gradually across the pad.

The method may be implemented such that the hardness of the pressuretuning feature changes stepwise across the pad.

The method may be implemented such that the pressure tuning featureincludes of concentric rings with different harnesses.

The method may be implemented such that the hardness of the pressuretuning feature decreases from the pad's center toward its perimeter.

The method may be implemented such that the change in the hardness ofthe pressure tuning feature across the pad is proportional to distancefrom the center of the pad.

The method may be implemented such that the backup pad has a nonplanarsurface where a pressure tuning feature with a uniform thickness ismounted on that surface.

The method may be implemented such that the nonplanar surface of thebackup pad is conical, hemispherical, or domed shape.

The method may be implemented such that the backup pad in combinationwith the pressure tuning feature causes the abrasive disc to haveimproved debris management compared to the abrasive disc on a backup padwith no pressure tuning feature.

The method may be implemented such that the backup pad in combinationwith the pressure tuning feature causes the abrasive disc to haveimproved heat management compared to the abrasive disc on a backup padwith no pressure tuning feature.

The method may be implemented such that the backup pad in combinationwith the pressure tuning feature causes the abrasive disc to haveimproved feature blending compared to the abrasive disc on a backup padwith no pressure tuning feature.

An abrading system that causes an abrasive disc to provide a patternedcut rate that includes a tool configured to drive movement of theabrasive disc. The system also includes a backup pad coupled to thetool. The system also includes a pattern feature. The pattern featurecauses the abrasive disc to exhibit a patterned cut rate when the toolis actuated. The patterned cut rate is different from a cut rateexhibited by the abrasive disc attached to the backup pad and toolwithout the pattern feature.

The system may be implemented such that the tool is a robotic tool. Thepattern feature is integrated into the tool.

The system may be implemented such that the pattern feature is a backuppad engaging surface of the tool.

The system may be implemented such that the pattern feature is aplurality of apertures in the backup pad engaging surface of the tool.

The system may be implemented such that the plurality of aperturesincludes a first set of apertures and a second set of apertures.

The system may be implemented such that the first set of apertures arecloser to an edge of the backup engaging surface of the tool than thesecond set of apertures.

The system may be implemented such that the first set of apertures havea first radius, the second set of apertures have a second radius, andthe first radius is larger than the second aperture.

The system may be implemented such that the apertures extend completelythrough the backup pad engaging surface of the tool.

The system may be implemented such that the pattern feature is a backuppad engaging portion of the tool coupled to a spindle. The backup padengaging portion is perpendicular to the spindle.

The system may be implemented such that the backup pad engaging portionhas a backup pad engaging surface with a first diameter, and aspindle-engaging surface with a second diameter. The first diameter islarger than the second diameter.

The system may be implemented such that an exterior edge of the backuppad engaging portion is angled from the spindle-engaging surface to thebackup pad engaging surface.

The system may be implemented such that the backup pad engaging surfaceincludes a scalloped edge.

The system may be implemented such that the backup pad engaging portionincludes a perimeter with a plurality of concave portions.

The system may be implemented such that the concave portions are equallyspaced about a circumference.

The system may be implemented such that the pattern feature causes abackup pad engaging portion of the tool to flex during an abradingoperation.

The system may be implemented such that the tool is a spindle configuredto engage a power tool.

The system may be implemented such that the pattern feature is coupledto both the tool, on a first side, and the backup pad, on a second side.

The system may be implemented such that the pattern feature includes afirst portion and a second portion.

The system may be implemented such that the first portion and secondportion are coplanar and coupled to both the tool and the backup pad.

The system may be implemented such that the first portion and the secondportion include different materials.

The system may be implemented such that the first and second portionsinclude compressible materials.

The system may be implemented such that the first and second portionsinclude incompressible materials.

The system may be implemented such that the pattern feature includes acompressible, cone-shaped feature.

The system may be implemented such that the pattern feature is coupledto the backup pad, on a first side, and is configured to couple to anabrasive article, on a second side.

The system may be implemented such that a cut rate of the system issubstantially uniform across a radius extending from a center of thebackup pad to an edge of the backup pad.

The system may be implemented such that a cut rate of the system has alocal maximum.

The system may be implemented such that the cut rate has at least twolocal maxima.

The system may be implemented such that the pattern feature iselastically deformable.

The system may be implemented such that the pattern feature ispositioned between the backup pad and the abrasive disc.

The system may be implemented such that the pattern feature includes amaterial having a hardness of less than about 60 Shore A.

The system may be implemented such that the pattern feature includes amaterial having a compressibility of less than about 170 psi at 25%deflection.

The system may be implemented such that the pattern feature includes amaterial made of a substantially incompressible material which has beenpatterned, 3D printed, embossed, or engraved.

The system may be implemented such that the pattern feature includes amaterial that is compressible.

The system may be implemented such that the pattern feature includes oneor more materials of a foam, an engraved, structured, 3D printed, orembossed elastomer, a fabric layer, a nonwoven layer, or a soft rubber.

The system may be implemented such that the pattern feature is made ofmultiple layers or multiple materials in a layered or agglomerateconstruction.

The system may be implemented such that the backup pad includes channelsextending from the surface of the damping feature to the opposite sideof the backup pad.

The system may be implemented such that the pattern feature includes amaterial having an elastic modulus of less than about 650 psi.

The system may be implemented such that the pattern feature has anonuniform thickness.

The system may be implemented such that the pattern feature has aconical cavity mounted on a conical surface of the backup pad.

The system may be implemented such that the hardness of the patternfeature changes across the backup pad from a center to a perimeter.

The system may be implemented such that the hardness of the patternfeature changes gradually across the backup pad.

The system may be implemented such that the hardness of the patternfeature changes stepwise across the backup pad.

The system may be implemented such that the pattern feature includes aplurality of concentric rings, each concentric ring having a differenthardness.

The system may be implemented such that the hardness of the patternfeature decreases from a center to a perimeter.

The system may be implemented such that the change in the hardness ofthe pattern feature across the backup pad is proportional to a distancefrom the center.

The system may be implemented such that the backup pad has a nonplanarsurface. The pattern feature is mounted to the nonplanar surface.

The system may be implemented such that the nonplanar surface of thebackup pad is conical, hemispherical, or domed shape.

A backup pad for an abrasive system is presented that includes a toolengaging feature. The backup pad also includes an abrasive articleengaging feature. The backup pad also includes a compressible featurethat changes a cut rate profile of an abrasive article attached to theabrasive article engaging feature.

The backup pad may be implemented such that the tool engaging feature ison a first side of the backup pad and the abrasive article engagingfeature is on a second side of the backup pad. The first side opposesthe second side.

The backup pad may be implemented such that the compressible feature iselastically deformable.

The backup pad may be implemented such that the compressible feature ispositioned between the backup pad and the abrasive disc.

The backup pad may be implemented such that the compressible featureincludes a material having a hardness of less than about 60 Shore A.

The backup pad may be implemented such that the compressible featureincludes a material having a compressibility of less than about 170 psiat 25% deflection.

The backup pad may be implemented such that the compressible featureincludes a material which has been patterned, 3D printed, embossed, orengraved to provide the desired deformability.

The backup pad may be implemented such that the compressible featureincludes a material that is compressible.

The backup pad may be implemented such that the compressible featureincludes a foam, an engraved, structured, 3D printed, or embossedelastomer, a fabric or nonwoven layer, or a soft rubber.

The backup pad may be implemented such that the compressible feature ismade of multiple layers and/or multiple materials in a layered oragglomerate construction.

The backup pad may be implemented such that the backup pad includeschannels extended from a surface of the damping feature to the oppositeside of the backup pad for dust and debris extraction.

The backup pad may be implemented such that the compressible featureincludes a material having an elastic modulus of less than about 650psi.

The backup pad may be implemented such that the compressible feature hasa nonuniform thickness.

The backup pad may be implemented such that the compressible feature hasa conical cavity mounted on a conical surface of the backup pad.

The backup pad may be implemented such that the hardness of thecompressible feature changes across the pad from its center toward itsperimeter

The backup pad may be implemented such that the hardness of thecompressible feature changes gradually across the pad.

The backup pad may be implemented such that the hardness of thecompressible feature changes stepwise across the pad.

The backup pad may be implemented such that the compressible featureincludes of concentric rings with different harnesses.

The backup pad may be implemented such that the hardness of thecompressible feature decreases from the pad's center toward itsperimeter.

The backup pad may be implemented such that the change in the hardnessof the compressible feature across the pad is proportional to distancefrom the center of the pad.

The backup pad may be implemented such that the backup pad has anonplanar surface where a compressible feature with a uniform thicknessis mounted on that surface.

The backup pad may be implemented such that the nonplanar surface of thebackup pad is conical, hemispherical, or domed shape.

The backup pad may be implemented such that the backup pad causes theabrasive disc to have improved debris management compared to theabrasive disc on a backup pad with no compressible feature.

The backup pad may be implemented such that the backup pad causes theabrasive disc to have improved heat management compared to the abrasivedisc on a backup pad with no compressible feature.

The backup pad may be implemented such that the backup pad incombination with the compressible feature causes the abrasive disc tohave improved feature blending compared to the abrasive disc on a backuppad with no damping feature.

A spindle for a robotic abrasive system that includes a tool-engagingshaft. The spindle also includes a backup pad engaging surface. Thebackup pad engaging surface includes a pressure tuning feature thatmodifies a pressure profile exerted by the backup pad against aworksurface.

The spindle may be implemented such that the tool-engaging shaft engagesa motive robotic arm.

The spindle may be implemented such that the motive robotic arm includesa force control unit.

The spindle may be implemented such that a controller adjusts the forcecontrol unit based on feedback received through the spindle.

The spindle may be implemented such that the pressure tuning featureincludes a plurality of apertures in the backup pad engaging surface.

The spindle may be implemented such that the plurality of aperturesextend completely through the backup pad engaging surface.

The spindle may be implemented such that the plurality of aperturescouple to a debris removal tool.

The spindle may be implemented such that the plurality of aperturesinclude a set of apertures arrange equidistant about the tool-engagingshaft.

The spindle may be implemented such that the set of apertures aresubstantially the same size.

The spindle may be implemented such that the set of apertures is a firstset of apertures. The plurality of apertures includes a second set ofapertures.

The spindle may be implemented such that the second set of apertureshave a second radius larger than a first radius associated with thefirst set of apertures.

The spindle may be implemented such that the backup pad engaging surfaceis on a first side of a tool portion that is perpendicular to thetool-engaging shaft. The tool portion engages the tool-engaging shaft ona second side that is opposite the first side. A thickness separates thefirst and second sides.

The spindle may be implemented such that the first side has a firstarea, the second side has a second area. A second area is smaller thanthe first area such that an edge connecting the first and second areaforms an angle with the backup pad engaging surface.

The spindle may be implemented such that the first area has a perimeterwith a plurality of indentations.

The spindle may be implemented such that the plurality of indentationsare regularly spaced about the perimeter.

The spindle may be implemented such that the backup pad engaging surfacehas a perimeter with a plurality of indentations.

The spindle may be implemented such that the plurality of indentationsare regularly spaced about the perimeter.

The spindle may be implemented such that the pressure tuning feature iselastically deformable.

The spindle may be implemented such that the pressure tuning feature ispositioned between the backup pad and the abrasive disc.

EXAMPLES

These Examples are merely for illustrative purposes and are not meant tobe overly limiting on the scope of the appended claims. Notwithstandingthat the numerical ranges and parameters setting forth the broad scopeof the present disclosure are approximations, the numerical values setforth in the specific examples are reported as precisely as possible.Any numerical value, however, inherently contains certain errorsnecessarily resulting from the standard deviation found in theirrespective testing measurements. At the very least, and not as anattempt to limit the application of the doctrine of equivalents to thescope of the claims, each numerical parameter should at least beconstrued in light of the number of reported significant digits and byapplying ordinary rounding techniques.

A combination of abrading experiments and Finite Element Analysis (FEA)modeling was used to compare performance attributes of abrasive backuppads described in the present disclosure to typical abrasive backup padswith uniform thickness flat foam layers. In each EXAMPLE the worksurfacebeing abraded by an abrasive pad was planar and parallel to the surfaceof the abrasive disc used in the EXPERIMENT. Abaqus commerciallyavailable software (SIMULIA™ by Dassault Systèmes®) was used to modelabrasive backup pads against worksurfaces is some EXAMPLES where it wasdifficult or impossible to measure attributes of the backup padsexperimentally.

Example 1

In this EXAMPLE the abrading performance of an abrasive backup paddescribed in this disclosure like what illustrated in FIGS. 2A-2C wasevaluated using FEA modeling. FIG. 2E shows an axisymmetric crosssection of the abrasive backup pad of this EXAMPLE worksurface. Anaxisymmetric FEA model with geometric parameters and material propertiesdescribed in Table 1 below was developed in Abaqus. Backup pad 280 and aflat worksurface, laying down parallel to and contacting surface 284 ofabrasive disc 286, are substantially harder than pressure tuning feature290 in this EXAMPLE. Thus, rigid body constraints have been applied tobackup pad 280 and the worksurface in the FEA model to reducecomputational time. The worksurface was fixed in its location as aboundary condition and a vertical displacement loading, parallel tocenter line 292, was applied to backup pad in the FEA model.

TABLE 1 Geometric parameters and material properties of axisymmetric FEAmodel of EXAMPLE 1 Pressure tuning 290 Abrasive disc 286 Height 294Height 296 Radius 272 Elastic modulus Poisson's Elastic modulusPoisson's (inch) (inch) (inch) (psi) ratio (psi) ratio 0.5 0.05 2.5 1000.1 5000 0.4

FIG. 11A shows the contact pressure profile between the abrasive pad andthe worksurface under 0.03-inch impression of the pad against theworksurface predicted by the FEA model. The contact pressure decreasesfrom the pad's center to its edge. FIG. 11B displays stress contour plotof the deformed abrasive backup pad under 0.03-inch impression of thepad against the worksurface predicted by the FEA model. As indicated,the uniform compression of the pressure tuning feature applies anon-uniform stress across the pressure tuning feature, higher close tothe center line of the pad and decreasing toward the edge of the pad,which causes a decreasing contact pressure between the abrasive disc andthe worksurface from the pad's center to its outer edge worksurface.

If this abrasive pad is rotating with an angular velocity of 60 RPMagainst the worksurface, with an assumed K_(p)=1 one can determine thematerial removal rate from the worksurface across the pad's surfaceusing the empirical Preston equation [I. F. W. Preston, J. Soc. Glass.Technol., 11, 214, 1927] shown below. FIG. 11C shows the variation ofthe material removal (cut) rate across the pad's surface. As indicated,the material removal rate of the abrasive disc of this EXAMPLE is almostuniform across the surface of the pad.

Material removal rate=K _(p) ×V×P:   Preston equation

-   -   K_(p): material constant    -   V: linear velocity    -   P: contact pressure

Comparative Example 1

In this EXAPLE the abrading performance of a typical abrasive backup padwith a uniform thickness foam layer mounted on a flat hard backup padwas evaluated using FEA modeling. FIG. 11D shows an axisymmetric FEAmodel of the abrasive backup pad of this EXAMPLE being used to abrade aflat worksurface, laying down parallel to and contacting the abrasivedisc.

FIG. 11E shows the contact pressure profile between the abrasive pad andthe worksurface under 0.03-inch impression of the pad against theworksurface predicted by the FEA model. The contact pressure is uniformacross the pad's surface. FIG. 11F displays the stress contour plot ofthe deformed abrasive backup pad under 0.03-inch impression of the padagainst the worksurface predicted by the FEA model. As indicated, thefoam layer deforms uniformly across the pad causing a uniform contactpressure between the abrasive disc ant the worksurface across the pad.

With uniform contact pressure across the whole pad's surface, and anincreasing linear velocity from center to outer edge, the materialremoval rate then increases from center to the outer edge (as indicatedschematically in FIG. 1C). If this abrasive pad is rotating with anangular velocity of 60 RPM against the worksurface, with an assumedK_(p)=1 one can determine the material removal rate from the worksurfaceacross the pad's surface using the empirical Preston equation. FIG. 11Gshows the variation of the material removal (cut) rate across the pad.

Comparing FIGS. 11C and 11G, one can conclude that the abrasive pad ofFIG. 2E applies a much more uniform cut rate on the worksurface acrossthe pad's surface. Comparing the area under these curves, which showsthe total cut from the worksurface, one can observe that the pad of FIG.2E removes more material from the worksurface compared to the typicalabrasive pad.

Example 2

In this EXAMPLE the abrading performance of an abrasive backup pad likethe pad illustrated in FIGS. 2A-2C was evaluated. A 5-inch diameter padwas made to test the concept of this pad in this disclosureexperimentally. The pad had a metallic conical backup pad including aspindle fabricated out of 6061 Aluminum and a pressure tuning featuremade of a multi-layered foam block with a conical cavity with the sameprofile as the conical backup pad. The foam block with cavity was madeof 20 layers of 3M™ Cushion-Mount™ Plus Plate Mounting Tape E1060H whichis a 0.06-inch thick double coated foam tape. The pad was made asfollows:

-   -   20 circular disks with 5-inch outer diameter were cut out of the        above Mounting Tape e using a laser cutting machine.    -   Using the same laser cutting machine circular holes with        appropriate diameters were cut out from 16 of 20 Mounting Tape        disks so that by laminating these 16 ring layers a conical        cavity with a profile similar to the conical backup pad was        made.    -   The 4 remaining intact Mounting Tape disks were laminated to        each other and then the stack lamination was adhered to the        bottom of the foam stack with cavity. At this point we had the        pressure tuning feature with the central cavity.    -   A layer of 3 mil thick double-sided Scotch VHB tape was adhered        to the whole surface of the conical side of the metallic backup        pad.    -   The pressure tuning feature was mounted from its cavity side        onto the VHB tape on the metallic conical backup pad.    -   A 3M NX Disc Coated Aluminum Oxide Disc—Very Fine Grade—P180        Grit—5 in Diameter—31217 was adhered from its PSA side to the        flat surface of the pressure tuning feature on the fabricated        pad.

FIGS. 12A-12D illustrate the abrasive pad article made according to theprocess described above. FIG. 12A illustrates a metallic conical backuppad with spindle. FIG. 12B illustrates the pressure tuning feature madeof multilayer foam block construction. FIG. 12C illustrates the abrasivepad assembly with an abrasive disc mounted on the free surface of thepressure tuning feature, and FIG. 12D illustrates a cutaway view takenalong section line 12D-12D illustrated in FIG. 12C.

Example 2 Abrasion Testing

The testing method consisted of loading the abrasive pad into a drillpress. The drill press was obtained from McMaster-Carr, part number:2799A21, which is an Economy Benchtop Drill Press with 120V AC, 13-¼″maximum worksurface diameter. The drill press drives abrasive pad into aworksurface that is fixed on typical work bench table chuck. Materialfrom the worksurface is removed during the drilling process. Specificsteps of the test procedure are as follows:

-   -   1. Place a worksurface, which is a MIC 6 cast aluminum 6″×6″        flat sheet 0.5″ in thickness (ground 6061 aluminum) on drill        press table. Fastened down the worksurface to drill press table        via 2 “C-clamps”    -   2. Set the drill press RPM (800 rpm) and duration of test (1        min).    -   3. Turn drill on and engage abrasive to the top surface of the        worksurface under a fixed given load (5 lbs).    -   4. Remove and clean the worksurface. After removing the abraded        worksurface from the drill table, the worksurface is clean with        blown air out of a high-pressure nozzle (100 psi). A hand towel        with water and IPA was used then to clean the worksurface of        abraded surface dust.    -   5. Place the worksurface into a Nanovea HS2000 3D Non-Contact        Profilometer and measure cut profile on its abraded worksurface.

FIG. 12E shows the cut profile of the worksurface abraded with theabrasive pad shown in FIGS. 12A-12D using the above test procedure. Asindicated, a uniform cut was applied on the worksurface across theabrasive pad.

Comparative Example 2

In this EXAMPLE the abrading performance of a typical abrasive backuppad with a uniform thickness foam block mounted on a flat backup pad,currently being used in abrasive processes, was evaluatedexperimentally. A 5-inch diameter pad was fabricated using the sameconstitutive materials used in EXAMPLE 2. This pad has a metallic flatbackup pad including a spindle fabricated out of 6061 Aluminum and aflat multi-layered foam block mounted on the flat surface of themetallic backup pad. The foam block was made of 7 layers of 3M™Cushion-Mount™ Plus Plate Mounting Tape E1060H. The steps to make thispad is as follows:

-   -   7 circular disks with 5-inch outer diameter were cut out of the        above Mounting Tape using a laser cutting machine.    -   All the circular disks made in the previous step were laminated        to each to make a cylindrical foam block.    -   A layer of 3 mil thick double-sided Scotch VHB tape was adhered        to the whole flat surface of the metallic backup pad.    -   The foam block was mounted on of its surface onto the VHB tape        on the flat backup pad.    -   A 3M NX Disc Coated Aluminum Oxide Disc—Very Fine Grade—P180        Grit—5 in Diameter—31217 was adhered from its PSA side to the        flat surface ofthe multi-layered foam block of the fabricated        pad apart from the metallic backup pad.        The resulting construction is illustrated in FIGS. 12F-12I. The        flat backup pad is illustrated in FIG. 12F, the multilayer foam        block in FIG. 12G, and the entire assembly in FIG. 12H. FIG. 12I        illustrates a cutaway view of the assembly of 12H along a        section lines 12I-12I. The same abrasion test procedure as the        one described in Example 2 Abrasion Testing above was used to        evaluate the abrading performance of the abrasive pad of this        EXAMPLE.

The resulting cut profile of the abrasive pad 12F is illustrated in FIG.12J. As illustrated, a nonuniform cut, increasing from the pad center toits edge, was applied on the worksurface across the abrasive pad.

Example 3

In this EXAPLE the abrading performance of an abrasive backup pad withconcentric rings pressure tuning feature like what illustrated in FIGS.3A and 3B in this disclosure was evaluated experimentally. A 5-inchdiameter pad was made to test the concept of this pad in thisdisclosure. The pad had a metallic flat backup pad including a spindlefabricated out of 6061 Aluminum, such as what illustrated in FIG. 12F,and a pressure tuning feature made of 3 rings, such as what illustratedin FIG. 3A. The pad was made as follows:

-   -   2 circular disks with 1.666-inch outer diameter were cut out of        Resilient Polyurethane Foam Sheet—Soft (0.25-inch thick,        Pressure to Compress 25% of 11 psi) obtained from McMaster-Carr,        part number: 86375K134 using a laser cutting machine.    -   The 2 circular disks made in the previous step were laminated to        each other using a layer of 3 mil thick double-sided Scotch VHB        tape. This laminate would be used as the central part of the        pressure tuning feature in the pad.    -   Using the same laser cutting machine a circular ring with a        1.666-inch inner diameter and a 3.333-inch outer diameter was        cut out of Resilient Polyurethane Foam Sheet—Ultra Soft        (0.5-inch thick, Pressure to Compress 25% of 3 psi) obtained        from McMaster-Carr, part number: 86375K114 using a laser cutting        machine. This ring would be used as the intermediate concentric        ring of the pressure tuning feature in the pad.    -   Using the same laser cutting machine another circular ring with        a 3.333-inch inner diameter and a 5-inch outer diameter was cut        out of Super-Cushioning Polyurethane Foam Circle (0.5-inch        thick, Pressure to Compress 25% of 0.3 psi) obtained from        McMaster-Carr, part number: 8883K54 using a laser cutting        machine. This ring would be used as the outer concentric ring of        the pressure tuning feature in the pad.    -   A layer of 3 mil thick double-sided Scotch VHB tape was adhered        to the whole flat surface of the metallic backup pad.    -   The circular laminate and the two concentric rings made in the        previous steps were mounted on of their surfaces onto the VHB        tape on the flat backup pad.    -   A 3M NX Disc Coated Aluminum Oxide Disc—Very Fine Grade—P180        Grit—5 in Diameter—31217 was adhered from its PSA side to the        flat surface of the concentric rings pressure tuning feature the        fabricated pad apart from the metallic backup pad. The pressure        tuning feature was mounted from its cavity side onto the VHB        tape on the metallic conical backup pad.    -   A 3M NX Disc Coated Aluminum Oxide Disc—Very Fine Grade—P180        Grit—5 in Diameter—31217 was adhered from its PSA side to the        flat surface of the pressure tuning feature on the fabricated        pad.

The same abrasion test procedure as the one described in Example 2Abrasion Testing above was used to evaluate the abrading performance ofthe abrasive pad of this EXAMPLE. The resulting cut profile of theabrasive pad of this EXAMPLE is illustrated in FIG. 13A. As illustrated,a nonuniform cut pattern was applied on the worksurface across theabrasive pad. The central portion of the abrasive pad removed the mostmaterial and the outer portion of the abrasive pad removed the leastmaterial from the worksurface while as illustrated in FIG. 12J, using atypical abrasive pad with a flat foam layer the cut rate increases fromthe pad's center toward its edge due to linear velocity increase towardthe pad's edge.

A FEA model of the abrasive pad of this EXAMPLE against a flatworksurface laying down parallel to the surface of abrasive disc wasthen developed. The same geometries were used for the metallic backuppad, the central foam disc and the concentric rings of the pressuretuning feature. Elastic moduli of 11, 3 and 0.3 psi as well as Poisson'sratios of 0.4, 0.1 and 0.1 were used as material properties of thecentral disc, intermediate and other concentric rings respectively inthe FEA model. Rigid body constraints were applied to the metallicbackup pad and the worksurface to reduce computational time as they weresubstantially harder than the pressure tuning feature. A compressiveload of 5 lbf was applied to the spindle of the backup pad against theworksurface while the worksurface was fixed in place. FIG. 13B shows theFEA predicted contact pressure profile between the abrasive pad and theworksurface. As illustrated the contact pressure was substantiallylarger in the central region of the disc above the central disc of thepressure tuning feature and it decreased toward the edge of the abrasivedisc. The reason behind this contact pressure profile lies in thedistribution of the hardness of materials used in the pressure tuningfeature which causes a significantly higher compressive stress in thecentral region of the disc than the regions above the concentric ringsas illustrated in FIG. 13C.

The materials used to make the pad of this EXAMPLES had been selectedarbitrary to just show the effect of hardness variation of the pressuretuning feature across the pad on the cut rate performance of the pad.However, by adjusting the number of concentric rings and their hardnessacross the pad, one can tune the cut pattern and obtain a desired cutprofile across the pad.

Example 4

In this EXAMPLE the abrading performance of an abrasive backup pad witha nonuniform surface like what illustrated in FIGS. 14A-14C in thisdisclosure was evaluated experimentally. A 5-inch diameter pad was madeto test the concept of this pad in this disclosure. The pad had ametallic backup pad including a conical surface on one side and a flatsurface with a spindle on the other side which was fabricated out of6061 Aluminum, such as the backup pad illustrated in FIG. 14A, and apressure tuning feature made of a foam layer with a uniform thickness of0.5-inch. The pad was made as follows:

-   -   A circular disk with 5-inch outer diameter were cut out of        Resilient Polyurethane Foam Sheet—Ultra Soft (0.5-inch thick,        Pressure to Compress 25% of 3 psi) obtained from McMaster-Carr,        part number: 86375K114 using a laser cutting machine.    -   A layer of 3 mil thick double-sided Scotch VHB tape was adhered        to the whole conical surface of the metallic backup pad.    -   The circular foam disc made in the previous steps was mounted on        of its surfaces onto the VHB tape on the conical backup pad.    -   A 3M NX Disc Coated Aluminum Oxide Disc—Very Fine Grade—P180        Grit—5 in Diameter—31217 was adhered from its PSA side to the        free surface of the pressure tuning feature of the fabricated        pad apart from the metallic backup pad.

The same abrasion test procedure as the one described in Example 2Abrasion Testing above was used to evaluate the abrading performance ofthe abrasive pad of this EXAMPLE. The resulting cut profile of theabrasive pad of this EXAMPLE is illustrated in FIG. 14D. As illustrated,a uniform cut pattern was applied on the worksurface across the abrasivepad. By engaging the abrasive pad against the worksurface the centralregion of the abrasive pad which was closer to the worksurface contactedthe worksurface first and the central region of the pressure tuningfeature was compressed to let the other areas on the abrasive disc comein to contact with the worksurface. Therefore, the central area of theabrasive disc was in contact the worksurface for a longer time duringthe abrasive prosses which led to a higher material removal from theareas close to the center of the pad. Also, the central region of thepad went under more compression which made this area harder than otherareas of the pad due to densification of the foam layer. This causedhigher contact pressure under the central area of the pad and adecreasing contact pressure profile toward the edge of the pad which inturn compensated the increasing linear velocity of the pad toward itsedge. Consequently, the pad made a uniform material removal from theworksurface across the pad.

1. A method of managing the contact pressure across an abrasive disc,the method comprising: coupling the abrasive disc to a backup padcomprising a pressure tuning feature that causes an experienced pressureby a worksurface, across a radius of the abrasive disc, to be uniform;abrading a worksurface by contacting the abrasive disc to theworksurface; and wherein the backup pad causes the abrasive disc to havea cut rate that is substantially uniform across the surface of theabrasive disc when compared to the abrasive disc on a backup pad with nopressure tuning feature.
 2. The method of claim 1, wherein the pressuretuning feature is elastically deformable.
 3. The method of claim 1,wherein the pressure tuning feature is positioned between the backup padand the abrasive disc.
 4. (canceled)
 5. The method of claim 1, whereinthe pressure tuning feature is made of multiple layers or multiplematerials in a layered or agglomerate construction.
 6. (canceled) 7.(canceled)
 8. The method of claim 1, wherein the pressure tuning featurehas a conical cavity mounted on a conical surface of the backup pad. 9.The method of claim 1, wherein the hardness of the pressure tuningfeature changes across the pad from its center toward its perimeter. 10.A backup pad for an abrasive system, the backup pad comprising: a toolengaging feature; an abrasive article engaging feature; and acompressible feature that changes a cut rate profile of an abrasivearticle attached to the abrasive article engaging feature. 11.(canceled)
 12. The backup pad of claim 10, wherein the compressiblefeature is elastically deformable.
 13. (canceled)
 14. The backup pad ofclaim 10, wherein the compressible feature comprises a material whichhas been patterned, 3D printed, embossed, or engraved to provide thedesired deformability.
 15. (canceled)
 16. The backup pad of claim 10,wherein the compressible feature is made of multiple layers and/ormultiple materials in a layered or agglomerate construction. 17.(canceled)
 18. The backup pad of claim 10, wherein the compressiblefeature includes a material having an elastic modulus of less than about650 psi.
 19. (canceled)
 20. (canceled)
 21. The backup pad of claim 10,wherein the hardness of the compressible feature changes across the padfrom its center toward its perimeter.
 22. (canceled)
 23. (canceled) 24.The backup pad of claim 21, wherein the compressible feature comprisesof concentric rings with different harnesses. 25-27. (canceled)
 28. Aspindle for a robotic abrasive system, the spindle comprising: atool-engaging shaft; a backup pad engaging surface; and wherein thebackup pad engaging surface comprises a pressure tuning feature thatmodifies a pressure profile exerted by the backup pad against aworksurface.
 29. The spindle of claim 28, and wherein the tool-engagingshaft engages a motive robotic arm.
 30. The spindle of claim 29, andwherein the motive robotic arm comprises a force control unit.
 31. Thespindle of claim 30, and wherein a controller adjusts the force controlunit based on feedback received through the spindle. 32-28. (canceled)39. The spindle of claim 29, wherein the backup pad engaging surface hasa perimeter with a plurality of indentations.
 40. The spindle of claim39, wherein the pressure tuning feature is positioned between the backuppad and the abrasive disc.